/* ----------------------------------------------------------------------
 * Project:      CMSIS DSP Library
 * Title:        arm_cfft_radix2_f32.c
 * Description:  Radix-2 Decimation in Frequency CFFT & CIFFT Floating point processing function
 *
 * $Date:        18. March 2019
 * $Revision:    V1.6.0
 *
 * Target Processor: Cortex-M cores
 * -------------------------------------------------------------------- */
/*
 * Copyright (C) 2010-2019 ARM Limited or its affiliates. All rights reserved.
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Licensed under the Apache License, Version 2.0 (the License); you may
 * not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an AS IS BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "arm_math.h"

void arm_radix2_butterfly_f32(
	float32_t *pSrc,
	uint32_t fftLen,
	const float32_t *pCoef,
	uint16_t twidCoefModifier);

void arm_radix2_butterfly_inverse_f32(
	float32_t *pSrc,
	uint32_t fftLen,
	const float32_t *pCoef,
	uint16_t twidCoefModifier,
	float32_t onebyfftLen);

extern void arm_bitreversal_f32(
	float32_t *pSrc,
	uint16_t fftSize,
	uint16_t bitRevFactor,
	const uint16_t *pBitRevTab);

/**
  @ingroup groupTransforms
 */

/**
  @addtogroup ComplexFFT
  @{
 */

/**
  @brief         Radix-2 CFFT/CIFFT.
  @deprecated    Do not use this function. It has been superseded by \ref arm_cfft_f32 and will be removed in the future
  @param[in]     S    points to an instance of the floating-point Radix-2 CFFT/CIFFT structure
  @param[in,out] pSrc points to the complex data buffer of size <code>2*fftLen</code>. Processing occurs in-place
  @return        none
 */

void arm_cfft_radix2_f32(
	const arm_cfft_radix2_instance_f32 *S,
	float32_t *pSrc)
{

	if (S->ifftFlag == 1U) {
		/* Complex IFFT radix-2 */
		arm_radix2_butterfly_inverse_f32(pSrc, S->fftLen, S->pTwiddle,
										 S->twidCoefModifier, S->onebyfftLen);
	} else {
		/* Complex FFT radix-2 */
		arm_radix2_butterfly_f32(pSrc, S->fftLen, S->pTwiddle,
								 S->twidCoefModifier);
	}

	if (S->bitReverseFlag == 1U) {
		/* Bit Reversal */
		arm_bitreversal_f32(pSrc, S->fftLen, S->bitRevFactor, S->pBitRevTable);
	}

}


/**
  @} end of ComplexFFT group
 */



/* ----------------------------------------------------------------------
 ** Internal helper function used by the FFTs
 ** ------------------------------------------------------------------- */

/**
  brief  Core function for the floating-point CFFT butterfly process.
  param[in,out] pSrc             points to in-place buffer of floating-point data type
  param[in]     fftLen           length of the FFT
  param[in]     pCoef            points to twiddle coefficient buffer
  param[in]     twidCoefModifier twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table
  return        none
 */

void arm_radix2_butterfly_f32(
	float32_t *pSrc,
	uint32_t fftLen,
	const float32_t *pCoef,
	uint16_t twidCoefModifier)
{

	uint32_t i, j, k, l;
	uint32_t n1, n2, ia;
	float32_t xt, yt, cosVal, sinVal;
	float32_t p0, p1, p2, p3;
	float32_t a0, a1;

#if defined (ARM_MATH_DSP)

	/*  Initializations for the first stage */
	n2 = fftLen >> 1;
	ia = 0;
	i = 0;

	// loop for groups
	for (k = n2; k > 0; k--) {
		cosVal = pCoef[ia * 2];
		sinVal = pCoef[(ia * 2) + 1];

		/*  Twiddle coefficients index modifier */
		ia += twidCoefModifier;

		/*  index calculation for the input as, */
		/*  pSrc[i + 0], pSrc[i + fftLen/1] */
		l = i + n2;

		/*  Butterfly implementation */
		a0 = pSrc[2 * i] + pSrc[2 * l];
		xt = pSrc[2 * i] - pSrc[2 * l];

		yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
		a1 = pSrc[2 * l + 1] + pSrc[2 * i + 1];

		p0 = xt * cosVal;
		p1 = yt * sinVal;
		p2 = yt * cosVal;
		p3 = xt * sinVal;

		pSrc[2 * i]     = a0;
		pSrc[2 * i + 1] = a1;

		pSrc[2 * l]     = p0 + p1;
		pSrc[2 * l + 1] = p2 - p3;

		i++;
	}                             // groups loop end

	twidCoefModifier <<= 1U;

	// loop for stage
	for (k = n2; k > 2; k = k >> 1) {
		n1 = n2;
		n2 = n2 >> 1;
		ia = 0;

		// loop for groups
		j = 0;
		do {
			cosVal = pCoef[ia * 2];
			sinVal = pCoef[(ia * 2) + 1];
			ia += twidCoefModifier;

			// loop for butterfly
			i = j;
			do {
				l = i + n2;
				a0 = pSrc[2 * i] + pSrc[2 * l];
				xt = pSrc[2 * i] - pSrc[2 * l];

				yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
				a1 = pSrc[2 * l + 1] + pSrc[2 * i + 1];

				p0 = xt * cosVal;
				p1 = yt * sinVal;
				p2 = yt * cosVal;
				p3 = xt * sinVal;

				pSrc[2 * i] = a0;
				pSrc[2 * i + 1] = a1;

				pSrc[2 * l]     = p0 + p1;
				pSrc[2 * l + 1] = p2 - p3;

				i += n1;
			} while (i < fftLen);                          // butterfly loop end
			j++;
		} while (j < n2);                           // groups loop end
		twidCoefModifier <<= 1U;
	}                             // stages loop end

	// loop for butterfly
	for (i = 0; i < fftLen; i += 2) {
		a0 = pSrc[2 * i] + pSrc[2 * i + 2];
		xt = pSrc[2 * i] - pSrc[2 * i + 2];

		yt = pSrc[2 * i + 1] - pSrc[2 * i + 3];
		a1 = pSrc[2 * i + 3] + pSrc[2 * i + 1];

		pSrc[2 * i] = a0;
		pSrc[2 * i + 1] = a1;
		pSrc[2 * i + 2] = xt;
		pSrc[2 * i + 3] = yt;
	}                             // groups loop end

#else /* #if defined (ARM_MATH_DSP) */

	n2 = fftLen;

	// loop for stage
	for (k = fftLen; k > 1; k = k >> 1) {
		n1 = n2;
		n2 = n2 >> 1;
		ia = 0;

		// loop for groups
		j = 0;
		do {
			cosVal = pCoef[ia * 2];
			sinVal = pCoef[(ia * 2) + 1];
			ia += twidCoefModifier;

			// loop for butterfly
			i = j;
			do {
				l = i + n2;
				a0 = pSrc[2 * i] + pSrc[2 * l];
				xt = pSrc[2 * i] - pSrc[2 * l];

				yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
				a1 = pSrc[2 * l + 1] + pSrc[2 * i + 1];

				p0 = xt * cosVal;
				p1 = yt * sinVal;
				p2 = yt * cosVal;
				p3 = xt * sinVal;

				pSrc[2 * i] = a0;
				pSrc[2 * i + 1] = a1;

				pSrc[2 * l]     = p0 + p1;
				pSrc[2 * l + 1] = p2 - p3;

				i += n1;
			} while (i < fftLen);
			j++;
		} while (j < n2);
		twidCoefModifier <<= 1U;
	}

#endif /* #if defined (ARM_MATH_DSP) */

}


void arm_radix2_butterfly_inverse_f32(
	float32_t *pSrc,
	uint32_t fftLen,
	const float32_t *pCoef,
	uint16_t twidCoefModifier,
	float32_t onebyfftLen)
{

	uint32_t i, j, k, l;
	uint32_t n1, n2, ia;
	float32_t xt, yt, cosVal, sinVal;
	float32_t p0, p1, p2, p3;
	float32_t a0, a1;

#if defined (ARM_MATH_DSP)

	n2 = fftLen >> 1;
	ia = 0;

	// loop for groups
	for (i = 0; i < n2; i++) {
		cosVal = pCoef[ia * 2];
		sinVal = pCoef[(ia * 2) + 1];
		ia += twidCoefModifier;

		l = i + n2;
		a0 = pSrc[2 * i] + pSrc[2 * l];
		xt = pSrc[2 * i] - pSrc[2 * l];

		yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
		a1 = pSrc[2 * l + 1] + pSrc[2 * i + 1];

		p0 = xt * cosVal;
		p1 = yt * sinVal;
		p2 = yt * cosVal;
		p3 = xt * sinVal;

		pSrc[2 * i] = a0;
		pSrc[2 * i + 1] = a1;

		pSrc[2 * l]     = p0 - p1;
		pSrc[2 * l + 1] = p2 + p3;
	}                             // groups loop end

	twidCoefModifier <<= 1U;

	// loop for stage
	for (k = fftLen / 2; k > 2; k = k >> 1) {
		n1 = n2;
		n2 = n2 >> 1;
		ia = 0;

		// loop for groups
		j = 0;
		do {
			cosVal = pCoef[ia * 2];
			sinVal = pCoef[(ia * 2) + 1];
			ia += twidCoefModifier;

			// loop for butterfly
			i = j;
			do {
				l = i + n2;
				a0 = pSrc[2 * i] + pSrc[2 * l];
				xt = pSrc[2 * i] - pSrc[2 * l];

				yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
				a1 = pSrc[2 * l + 1] + pSrc[2 * i + 1];

				p0 = xt * cosVal;
				p1 = yt * sinVal;
				p2 = yt * cosVal;
				p3 = xt * sinVal;

				pSrc[2 * i] = a0;
				pSrc[2 * i + 1] = a1;

				pSrc[2 * l]     = p0 - p1;
				pSrc[2 * l + 1] = p2 + p3;

				i += n1;
			} while (i < fftLen);                   // butterfly loop end
			j++;
		} while (j < n2);                      // groups loop end

		twidCoefModifier <<= 1U;
	}                             // stages loop end

	// loop for butterfly
	for (i = 0; i < fftLen; i += 2) {
		a0 = pSrc[2 * i] + pSrc[2 * i + 2];
		xt = pSrc[2 * i] - pSrc[2 * i + 2];

		a1 = pSrc[2 * i + 3] + pSrc[2 * i + 1];
		yt = pSrc[2 * i + 1] - pSrc[2 * i + 3];

		p0 = a0 * onebyfftLen;
		p2 = xt * onebyfftLen;
		p1 = a1 * onebyfftLen;
		p3 = yt * onebyfftLen;

		pSrc[2 * i] = p0;
		pSrc[2 * i + 1] = p1;
		pSrc[2 * i + 2] = p2;
		pSrc[2 * i + 3] = p3;
	}                             // butterfly loop end

#else /* #if defined (ARM_MATH_DSP) */

	n2 = fftLen;

	// loop for stage
	for (k = fftLen; k > 2; k = k >> 1) {
		n1 = n2;
		n2 = n2 >> 1;
		ia = 0;

		// loop for groups
		j = 0;
		do {
			cosVal = pCoef[ia * 2];
			sinVal = pCoef[(ia * 2) + 1];
			ia = ia + twidCoefModifier;

			// loop for butterfly
			i = j;
			do {
				l = i + n2;
				a0 = pSrc[2 * i] + pSrc[2 * l];
				xt = pSrc[2 * i] - pSrc[2 * l];

				yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
				a1 = pSrc[2 * l + 1] + pSrc[2 * i + 1];

				p0 = xt * cosVal;
				p1 = yt * sinVal;
				p2 = yt * cosVal;
				p3 = xt * sinVal;

				pSrc[2 * i] = a0;
				pSrc[2 * i + 1] = a1;

				pSrc[2 * l]     = p0 - p1;
				pSrc[2 * l + 1] = p2 + p3;

				i += n1;
			} while (i < fftLen);                      // butterfly loop end
			j++;
		} while (j < n2);                        // groups loop end

		twidCoefModifier = twidCoefModifier << 1U;
	}                             // stages loop end

	n1 = n2;
	n2 = n2 >> 1;

	// loop for butterfly
	for (i = 0; i < fftLen; i += n1) {
		l = i + n2;

		a0 = pSrc[2 * i] + pSrc[2 * l];
		xt = pSrc[2 * i] - pSrc[2 * l];

		a1 = pSrc[2 * l + 1] + pSrc[2 * i + 1];
		yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];

		p0 = a0 * onebyfftLen;
		p2 = xt * onebyfftLen;
		p1 = a1 * onebyfftLen;
		p3 = yt * onebyfftLen;

		pSrc[2 * i] = p0;
		pSrc[2 * l] = p2;

		pSrc[2 * i + 1] = p1;
		pSrc[2 * l + 1] = p3;
	}                             // butterfly loop end

#endif /* #if defined (ARM_MATH_DSP) */

}
